I'm no expert so I don't know what causes more damage, but the production of photovoltaic cells also is by no means environmentally friendly. People die, ecosystems get destroyed, ...

And people argue that birds fly into wind generators and die, idk how much damage that is comparatively but probably the least. So from an environmental perspective, as a layman, I'd rank them wind > water > sun > non-renewables (nuclear > gas > coal).

But wind (and sun) always changes, so it's impossible to only have wind (and sun). You need:

• Something stable that carries a large percentage (for example water in rivers or at the end of lakes (so basically at the start of a river)).

• Something flexible that can quickly be increased or decreased (for example pumped hydro storage power stations, bonus points there for also being able to use energy when there's too much wind/sun; or non-renewables (burn more gas, get more electricity))

So even if we assume that wind and sun are better than water we still need either water or non-renewables. I'd say that's an easy choice.

We already had so much of it, the renewable targets would have been too easy? Most dams use huge amounts of concrete or earth moving, and there’s no carbon-free way to do that work at this time? Policy makers didn’t want to incentivize any dam construction?

These are guesses. It’s probably in some kind of records. Sometimes laws even explain the rationale in the beginning with a bunch of “whereas” statements. But I’m too lazy to look it up right now.